The ongoing battle between social-media companies and covid-19 misinformation pushers—including US president Donald Trump—stepped up again this week thanks to a new viral video. And it has exposed, once again, how difficult addressing conspiracy theories is for Facebook, Twitter, and others.

The latest video comes from a group called America’s Frontline Doctors, which is sponsored by the right-wing Tea Party Patriots. It features a professional-looking group of people in white lab coats advocating hydroxychloroquine, the malaria treatment previously pushed by the president. One doctor speaking at the press conference promoted the drug as a “cure” for the coronavirus, and said that people “don’t need” to wear masks.  The FDA withdrew its emergency-use authorization for hydroxychloroquine for treating covid-19 patients in June, after establishing that the drug was not effective and potentially dangerous. 

The video’s false claims led to removals on Facebook, YouTube, and Twitter for violating policies on health misinformation. Donald Trump Jr.’s Twitter account was temporarily limited after he shared it, and a retweet by the president himself was deleted. By the time that happened, however, the video had already been seen by millions of people.

The success of America’s Frontline Doctors and Plandemic, another covid-19 conspiracy video, which became a big hit in May, show how challenging it is to combat a misinformation ecosystem that has remained largely unchecked for years. Why is this happening now?

Misinformation peddlers are getting better at finding big audiences. Conspiracy theories are typically seen as thriving at the wild fringes of online thought. But that’s not really how some of the more successful videos have spread over the past few months. Prominent figures in the anti-vaccine movements began seeking out audiences with larger, more mainstream YouTubers to get their beliefs in front of larger audiences. 

Also helping? Media coverage, whether sympathetic or outraged. The doctors’ press conference was livestreamed by Breitbart, with the caption, “BREAKING: American Doctors Address COVID-19 Misinformation with SCOTUS Press Conference” before the post was deleted. Breitbart has more than 4.5 million Facebook followers. 

Takedowns can boost—not block—the cycle. Some far-right figures have, for years, claimed that technology platforms  are secretly conspiring to silence conservative political thought. As soon as the press conference started disappearing from mainstream social media, supporters began to re-upload new copies of the video and share it. By then it had added appeal as a video that mainstream forces “don’t want you to see.” This makes it more likely to be seen by those who already don’t trust these institutions, exacerbating the problem.

Increased enforcement may be coming too late. Although the tactics used to slow down conspiracies may have some minor successes, they have happened so late that prevention may be impossible. We reported recently that experts believe it could be too late to stop the conspiracy group QAnon with fact checks and account bans.